Beijing and Washington attempted to revive long-stalled nuclear negotiations to disarm North Korea, with the two sides holding direct talks in Geneva and China's vice-premier visiting Pyongyang.
The US team led by outgoing special representative Stephen Bosworth, and his replacement Glyn Davies on Monday sat down at the US mission with North Korea's delegation led by first vice minister Kim Kye-Gwan, for their second round of talks in three months.
After a day of "very intensive discussions", Bosworth said: "I think we are moving in a positive direction. We have narrowed some differences but we still have differences that we have to resolve."
He added there has been "some progress" and that the talks would resume Tuesday.
Separately, China's vice premier Li Keqiang travelled to Pyongyang, where he met North Korean leader Kim Jong-Il, state media said.
Kim told Li that Pyongyang "hopes the six-party talks about the nuclear issue on the Korean peninsula should be restarted as soon as possible", China's official Xinhua news agency reported early Tuesday.
The "principle of simultaneous action" should apply, it quoted Kim as saying -- a reiteration of the North's stance that the negotiations should begin again without preconditions.
The North formally quit the six-party forum in April 2009, a month before staging its second atomic weapons test. It has since repeatedly said it wants to come back, but Washington is demanding a physical sign of sincerity first.
Li, widely expected to be China's next premier, said Beijing was "working for positive achievements, creating conditions for reopening the six-party talks at an early date", Xinhua said.
China, which is Pyongyang's closest ally and a major economic partner, has hosted the six-party forum since 2003, which includes the two Koreas, Russia, the United States and Japan.
However, analysts see no breakthrough for the six-party talks coming during the Geneva meeting. Rather, they see engagement between the two parties as a way to stop Pyongyang from making rash moves.
"The view is that while they are talking, they are not provoking -- it's jaw-jaw rather than war-war," Mark Fitzpatrick, who heads the non-proliferation program at the International Institute for Strategic Studies, told AFP.
"I don't think that people will say this is a disaster because there is nothing concrete in terms of results," he added.
Ahead of the meeting, a senior State Department official said "our concern is that if we don't engage, that could result in miscalculations by the North Koreans, as we have seen in the past."
However, the US stressed it would not return to long-stalled six-party talks unless the North made a "clear commitment ... on the denuclearization side."
Bosworth said the goal of the Geneva talks was "to find a solid foundation on which to launch a resumption of discussions both bilateral and multilateral, and we will continue to work hard to bring that about."
Analysts believe that the North, which has insisted on the resumption of the six-way talks without pre-conditions, would not make a concession at the Geneva meeting.
In September 2005, the North agreed to abandon all nuclear weapons and programs in return for security guarantees, energy aid and a peace pact formally ending the 1950-53 war and diplomatic ties with the United States.
In 2007 it shut its plutonium-producing Yongbyon reactor. But during the following year the process began to melt down amid mutual accusations of bad faith.
In April 2009 Pyongyang walked out of the six-party forum, a month before staging its second atomic weapons test.
The North's deadly artillery attack last November on a South Korean island further complicated efforts to restart nuclear dialogue.
But a surprise meeting between nuclear envoys of South and North Korea on the sidelines of an Asian security conference in Bali, Indonesia led to the first round of direct US-North Korea talks in New York in July.
The second set of discussions is coming just as the two parties agreed to resume searches for the remains of Americans killed in the 1950-53 Korean War after a six-year hiatus, in a further sign of easing tensions between the two sides.